1. Field of the Invention
The present invention relates to an ink-jet recording apparatus for forming an image on a recording material by discharging ink, and a method for operating the same. For example, the invention relates to an ink-jet recording apparatus that has subtanks, each for holding a relatively small amount of ink to be supplied to an ink-jet recording head that has integrally formed nozzles (discharge ports) for discharging ink liquids of a plurality of colors, and in which ink is replenished from a main tank to a corresponding subtank while printing is not performed when the amount of ink remaining within the subtank becomes small, and a method for operating the ink-jet recording apparatus. The invention also relates to an ink-jet recording apparatus in which ink is supplied to a recording head moved to an ink replenishing mechanism provided outside of a printing range when it has been detected that the remaining amount of ink becomes small during a printing operation, and a method for operating the ink-jet recording apparatus.
Particularly, the present invention relates to improvement of a method for operating an apparatus for injecting ink by an ink replenishing mechanism when the amount of ink remaining within a subtank decreases, and allows maintenance of stable ink supply when executing ink replenishment and stability of printing after ink supply. It is preferable to provide a joint portion for preventing leakage of ink between the recording head and the ink supply mechanism, and to prevent entrance of a gas or dust from the outside.
2. Description of the Related Art
In an ink-jet recording apparatus, ink is supplied to a recording head, and an image is formed by providing a pattern made of ink dots on a recording material, such as paper or the like, by driving ink-droplet discharge means, such as piezoelectric elements, electrothermal transducers or the like, provided in the recording head based on image data. A recording head for obtaining a color image usually has discharge ports for discharging ink droplets of different colors, such as yellow, magenta, cyan and black. In a scanning-type recording apparatus, the above-described recording head is mounted on a carriage reciprocating in predetermined directions along a recording medium. Usually, one head has one type of ink, and, in most cases, a plurality of heads are arranged in a main scanning direction.
However, since it is disadvantageous to have a plurality of heads as described above, from the viewpoint of the cost and the size of the apparatus, heads have been devised in each of which discharge ports of ink liquids of a plurality of colors are integrated. A recovery operation for such a head may be executed using individual caps, recovery means or the like. However, since provision of individual components is disadvantageous from the viewpoint of the cost and the size, execution of a simultaneous recovery operation for nozzles for ink liquids of a plurality of colors with a common cap has been proposed. In this case, when a recovery operation becomes necessary, all of nozzles for ink liquids of a plurality of colors are simultaneously subjected to a recovery operation.
Reduction of the size of an ink tank integrally formed with a head unit will result in reduction of the number of printable sheets, and consumption of ink during a printing operation may occur. In order to solve such problems, an ink-remaining-amount sensor may be provided within the ink tank. Anyway, in order to manage the amount of ink, the amount of ink must be maintained by estimating the maximum amount of ink required for images to be printed.
It has been known, in a head in which discharge ports of ink liquids of a plurality of colors are integrated and an ink tank integrally configured with the head, to supply ink by exchange of an ink cartridge or a replenishing mechanism of ink after an ink liquid of a particular color has been completely consumed. In a recording head in which ink liquids of a plurality of colors are provided on the same plane, when ink is supplied from a main tank to a subtank integrally mounted with a head, ink liquids of respective colors discharged onto a recording sheet are mixed to produce color mixture.
Usually, a subtank has means for maintaining a negative pressure generated as ink used during a printing operation is being consumed in an equilibrium condition. For example, in a sponge-type ink tank, an equilibrium condition can be maintained by taking air from a hole communicating with the atmospheric air that is provided in a tank receptacle, in place of ink consumed from the ink tank.
A bag-shaped raw ink tank made of an aluminum sheet or the like contains ink. Such a raw ink tank has means for generating a predetermined negative pressure, so that as the amount of ink within the raw ink tank is reduced, a negative-pressure state within the raw ink tank can be maintained within a predetermined range, for example, by contraction of the bag.
When replenishing ink from a main tank to an ink tank (hereinafter termed a “subtank”) connected to the head by an ink replenishing mechanism, for example, the main tank may be pressurized (for example, as disclosed in Japanese Patent Application Laid-Open (Kokai) No. 7-32606 (1995), or a suction operation may be executed via the head (for example, as disclosed in Japanese Patent Application Laid-Open (Kokai) No. 59-207259 (1984)).